These are the most popular games on Steam - report

The most popular games on dominant PC download platform Steam are Valve's, with Dota 2 revelling in an estimated 25.9 million owners, and Team Fortress 2 an estimated 20.3 million owners.

That's according to Ars Technica, which has been randomly polling a public user base of 172 million Steam Community IDs for two months to come up with its results. There's a much more detailed explanation of how it works on Ars Technica.

The top 20 games are almost all Valve made: Half-Life 2 add-on Lost Coast has nearly 13 million estimated owners, Counter-Strike: Source nearly 12 million and Half-Life 2: Deathmatch 11 million.

The exceptions are Skyrim in 14th place with 5.94 million estimated owners, Civilization 5 in 16th with 5.84 million estimated owners and Garry's Mod in 18th with 5.35 million estimated owners.

However, the graph changes significantly when you measure how many of those owned games have actually been played. Ars Technica worked out that nearly 37 per cent of all owned games on Steam remain unplayed and sit in digital libraries collecting digital dust.

Indeed, as many of the top 20 are free or downloaded as a matter of 'oh I may as well' or 'it was a gift' or 'it was part of a sale' - rather than 'I intend to buy and play this now' - things start to make more sense.